The project studies have been conducted for the five systems, especially aiming to clarify the Subーstituent electronic effects in a higher order approximation : (1) ^<17>O and ^<15>N nmr SCS (substituent chemical shift) of 4'-substituted -NNO- azoxybenzenes (AZOXY), (2) ^<15> nmr SCS of (4-substituted benzylidene) phenylamine-N-oxides (NITRON), (3) solid state ^<195>Pt and ^<13>C nmr SCS of 1-(4-substituted pyridine 1-oxide)-3-ethylene-2, 4-dichloro-platinum (II) complexes (PYNOPT), and further, (4) ^<17>O and ^<15>N nmr SCS of 3- and 4-substituted pyridine 1-oxides (PYNO), and (5) substituent effects on basicities of the PYNO derivatives.The nmr SCSs of the entire systems, except for the PYNOPT one, can be best described in terms of the LSFE equation allowing the duality of resonance effects. The importance of such duality has been demonstrated for understanding the general electronic substituent effects of these hetero aromatic systems having N-O dative bonds. In the PYNOPT system, more reliable data, especially solid state ^<17>O and ^<15>N nmr SCS, have been waited for future analysis.